The present invention relates to an iron golf club set composed of a plurality of golf clubs having steel shafts. More specifically, the present invention relates to an iron golf club set adapted to facilitate swinging for the entire club set, particularly realizing easy rising of a ball when it is hit by a longer golf club, and easy control of the direction of a ball when it is hit by a shorter golf club.
For a shaft of an iron golf club, a steel shaft having a steel pipe formed in a tapered shape has been used. As methods used to manufacture steel shafts corresponding to respective counts when an iron golf club set is made using such steel shafts, a stretching process, a chip-cutting process, and so on, have been available.
The stretching process is a method comprising the steps of preparing raw material pipes (base pipes) equal in weight for a plurality of golf clubs; and stretching the raw material pipes until they reach lengths corresponding to respective counts while forming step patterns (node-shaped patterns appearing in shaft axial directions) on outer circumferential surfaces of the raw material pipes by using a plurality of dies different in inner diameters. On the other hand, the chip-cutting process is a method comprising the steps of preparing a plurality of steel shafts stretched to a predetermined length while forming step patterns on outer circumferential surfaces of raw material pipes; and cutting the tip portions of these steel shafts corresponding to the lengths of respective counts such that the steel shafts can be formed to have necessary lengths. Each of the step patterns generally includes a plurality of steps formed at a predetermined interval along the shaft axial direction.
However, in the case of the stretching process, all the steel shafts in the golf club set are constant in mass, the shafts stretched relatively long for the long clubs are thin, and the shafts stretched relatively short for the short clubs are thick. Thus, the long club gives a heavy feeling to a golfer, while the short club gives a light feeling to the golfer. On the other hand, in the case of the chip-cutting process, the shafts for the short clubs are substantially lighter in mass.
If the long golf clubs were felt to be heavy in relative relation, then swinging for the long clubs became difficult, resulting in difficult rising of a ball. If the short golf clubs were felt to be light in relative relation, then controlling of a direction of a ball hit by the short golf club became difficult. As a result, the use of the iron golf club set composed of the plurality of golf clubs made of steel shafts was difficult for those other than professional golfers or highly skilled players.